Lubricant injection system

ABSTRACT

A lubricant supply line from a lubricant pump supplies a number of serially connected injectors, each of which has a connection with a bearing to be lubricated. A timing arrangement cyclically starts and stops the pump to supply and to release pressure in the lubricant supply line. Each injector is constructed so that, when the inlet pressure thereto rises, an accurately measured amount of lubricant is forced to its bearing connection and the risen inlet pressure is serially applied to the next injector in the series so that it subsequently forces a like measured amount of lubricant to its bearing connection. An accumulator is connected to the outlet of the last injector and becomes operative after the last injector has functioned. Thereafter the pump stops to release built-up pressure which causes serial recharging of the injectors to ready them for accurately measured lubrication during the next cycle. During this recharging event, only the first injector returns a relatively small amount of lubricant to the pump and each injector receives its recharge from the next one, except the last one which receives its recharge from the accumulator. The accumulator also serves as a malfunction indicator for the system.

United States Patent [72] Inventor JeromeB.Wegmann St. Louis County, Mo.[2]] Appl. No. 876,358 [22] Filed Nov. 13, I969 [45] Patented Sept. 28,1971 [73] Assignee McNeil Corporation Akron, Ohio [54] LUBRICANTINJECTION SYSTEM 10 Claims, 7 Drawing Figs.

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[56] References Cited UNITED STATES PATENTS 1,198,173 9/1916 Wakefield184/56 2,463,552 3/l949 Newhall 417/346 X Primary Examiner-Robert M.Walker Att0rney-Koenig, Senniger, Powers and Leavitt ABSTRACT: Alubricant supply line from a lubricant pump supplies a number ofserially connected injectors, each of which has a connection with abearing to be lubricated. A timing arrangement cyclically starts andstops the pump to supply and to release pressure in the lubricant supplyline. Each injector is constructed so that, when the inlet pressurethereto rises, an accurately measured amount of lubricant is forced toits bearing connection and the risen inlet pressure is serially appliedto the next injector in the series so that it subsequently forces a likemeasured amount of lubricant to its bearing connection. An accumulatoris connected to the outlet of the last injector and becomes operativeafter the last injector has functioned. Thereafter the pump stops torelease built-up pressure which causes serial recharging of theinjectors to ready them for accurately measured lubrication during thenext cycle. During this recharging event, only the first injectorreturns a relatively small amount of lubricant to the pump and eachinjector receives its recharge from the next one, except the last onewhich receives its recharge from the accumulator. The accumulator alsoserves as a malfunction indicator for the system.

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PATENTED SEP28 |97l SHEET 3 OF 4 LUBRICANT INJECTION SYSTEM BACKGROUNDOF THE INVENTION Injectors have heretofore been arranged for multipleinjection of measured amounts of lubricant to various bearings. Theyemployed individual accumulators for measuring amounts to be delivered.The multiplicity of accumulators was costly and they requiredelastomeric seals which were undesirable in high temperature locationsof the injectors on hot machinery. Moreover, in former arrangementsduring each cycle each injector-vented lubricant in parallel with theothers all the way back to the sump of the pump. This wasted ventingtime and required much costly piping. According to the present inventiona single accumulator is used in connection with the last injector of aseries of them, and when the accumulator vents, each injector vents asmall measured volume a short distance to the preceding injector, withthe exception of the first injector which is the only one which ventsback to the pump, thus saving accumulator and piping costs as well asimproving perforrnance and operating speed. At a given speed ofoperation more injectors can be connected to a given pump. Otheradvantages will be apparent from the following descriptron.

SUMMARY The gist of the invention is in the connection of injectors andan accumulator in serial order, such that the first injector ispressurized from a timed lubricant pump and then the others arepressurized in order, to perform injections, the accumulator beingfinally pressurized and charged. Upon venting at the pump, the injectorsare vented in the same serial order. Only the first one returnslubricant back to the pump as it is recharged by bleedback from thesecond injector. Then the third one bleeds back to the second rechargingit. This sequence of events continues throughout the series until theaccumulator is reached which forces lubricant back to the last injectorin the series to recharge it. Thus all of the injectors are rechargedbut only the first is required to return lubricant to the pump uponventing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevationillustrating a typical complete system made according to the invention;

FIG. 2 is a vertical section through a lubricant pump of the systemwhich is shown as part of FIG. 1;

FIG. 3 is an enlarged axial section of line-venting parts at the outletof the pump;

FIG. 4 is an enlarged axial section of several injectors and anaccumulator; and

FIGS. 5-7 are views illustrating operating events.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

PREFERRED EMBODIMENT OF THE INVENTION Referring to FIG. 1, numeral 1indicates a solenoid operated three-way air supply and vent valve. Itsoperating solenoid 3 is excited and deexcited at intervals by anadjustable electric timing switch 5. The connecting wiring is shown at4. These parts are shown diagrammatically, being known per se. Thus theair valve 1 is opened and closed at adjustably timed intervals accordingto the timing adjustment of switch 5. A compressed air supply line 7feeds valve 1. The valve is connected to a pump 9 by air line 11. Whenthe valve 1 is closed it vents line 11, and when open supplies pump 9with air at a nominal pressure, for example at 40 to 50 p.s.i.

The pump 9 is detailed in FIGS. 2 and 3. It comprises an air cylinder 13having a sealed upper head 15. The air line 11 connects at 14 with thelower end 12 of cylinder 13. In the cylinder 13 is an air operatedpiston 17 biased downwardly from the head 15 by a return spring 19.Above piston 17 is an atmospheric relief passage 20. In a gland portion18 of the head 15 is located a packing 22 around a plunger 21. Plunger21 is connected to the piston 17 at 16.

Threaded into the gland portion 18 is the threaded end 23 of a pumpcylinder 25. The end 23 confines the packing 22. The plunger 21reciprocates in cylinder 25. Threaded to the outside of the upper end ofthe cylinder 25 is a nut 27 which bears on a head 29 of a lubricantsupply cylinder 31. The lower end of cylinder 31 is sealed to head 15 bya washer 24.

In the cylinder 31 is a lubricant follower piston 33. A hub 35 of piston33 slides on the outside of cylinder 25, being sealed by packing 30. Thepiston 33 is biased downwardly by a spring 37. Ports for admission andexit of air above piston 33 are shown at 39. Lubricant is carried underpiston 33 as indicated by stippling. A minimum amount is shown in FIG.2. The lubricant has access to the inside of cylinder 25 through lowerports 26 in the latter.

At 43 is shown a conventional lubricant charging nipple connected to apassage 45 leading to the bottom of cylinder 31. In the passage 45 is astrainer 47 from the inside of which is connected a port 49 which leadsto a threaded openable drain plug 51. The nipple 43 contains aconventional one-way check valve (not shown) to admit lubricant.

Threaded into the inside upper end of cylinder 25 is an outlet nipple53. Threaded into an inner shoulder 55 of this nipple 53 (see also FIG.3) is a valve body 57 which has an outer shoulder 59 engaging a gasket63 on an inner shoulder 61 of cylinder 25. Body 57 is held in place byan inner sleeve 54 of the nipple 53. An O-ring 56 seals body 57 to thepart 54 of nipple 53. Above the O-ring the body 57 is arranged withradial clearance 62 inside of the nipple 53 for accommodating flow oflubricant. The body 57 has an axial passage 65 through it. It also haslower and upper cross ports 67 and 69. Port 67 terminates in aperipheral groove 71 which contains a constrictive elastomeric sleeve 72forming a ring check valve pen mitting outward flow from passage 67 toclearance 62 but not the reverse, thus functioning as a reverse checkvalve. Located in the passage 65 (between the transverse ports 67 and69) is a spring-pressed ball check valve 73 which checks against egressto nipple 53 of lubricant but permits ingress of lubricant to thecylinder 25. The spring of ball valve 73 is numbered 74. The spring 74and the ball valve 73 are held in place by an inlet nipple 75 threadedinto the lower end of the body 57.

Operation of the pump 9 is as follows: First it is primed (FIGS. 2 and3). This is accomplished by connecting a lubricant supply under pressureto nipple 43. This infills the space under follower piston 33 pushing itup against action of spring 37 until hole 39 is crossed and lubricantweeps out indicating a full condition. Ring check valve 72 holds againsta greater lubricant pressure than is supplied by action of spring 37 onpiston 33. Hence, until the pump starts no lubricant is discharged tothe remainder of the system.

Upon starting the pump lubricant is pumped from under piston 33,entering cylinder 25 via ports 26. The pump forces it up into thecentral passage 65 of body 57 via nipple 75, from whence it escapesradially out through cross port 67, through ring check valve 72,clearance 62, inward through cross port 69 and then out from the centralpassage 65 to nipple 53. This supplies lubricant under pressure to theremainder of the system to be described. Discharge through body 57 tonipple 53 occurs when the plunger 21 is pushed up by piston 17. Theratio of the area of piston 17 to the end area of plunger 21 is madelarge enough so that a pressure which is greater than priming pressureis obtained under a nominal air pressure in air line 11. This pressuremay be on the order of 800 to 1,000 p.s.i. or more, for example. Whenthe air in line 11 is vented, the piston 17 and plunger 21 are retractedunder expanding action of spring 19 to receive in cylinder 25, first,through check valve 73 a small measured amount (to be described) ofreturned lubricant from a first injector in the system, and second, anadditional amount through ports 26 when the plunger 21 reaches thebottom of its stroke. The latter amount is equal to the total amount oflubricant which has been ejected by all injectors in the system duringthe preceding cycle of its operation, as will appear below.

Referring again to FIG. 1, the nipple 53 will be seen to be connectedwith a lubricant line 77 which feeds an inlet nipple 79 of a first oneof a series of identical connected injectors 81. The number of injectorsin the series is arbitrary, three being shown for example in FIG. 1, thebreak lines 82 indicating that more may be included in the series. Anoutlet nipple 83 of each injector 81 connects with the inlet nipple 79of the next one, except as to the last one in the series, the outletnipple 83 of which connects with the inlet 85 of an accumulator 87 (seeFIGS. 1 and 4). FIG. 4 shows details of the accumulator and of the lasttwo injectors of a series of them. Coupling nuts are shown at 94.

Each injector 81 (FIG. 4) is in the form of a manifold composed of ahollow body 89 to which is threaded an upper hollow cap 90 and a lowerfitting 91, the latter being for the attachment as shown of a branchlubricant line 93 (FIGS. 1 and 4). Lines such as 93 lead to machinebearings (not shown) to be lubricated by the system under the statedhigh pressure of 800 to 1,000 p.s.i. for example. Each fitting 91 holdsin place the seat 95 of a spring pressed ball check valve 97 supportedin the fitting 91. The spring is numbered 92.

Each manifold body 89 is also formed with a dividing mid portion 99 ofcylindric form in which slides a piston 101. An extension 103 from theupper side of piston 101 has a head 107. The unbalanced pressuretransmitting area 100 of the upper end of head 107 equals the lower endarea of the piston 101. The outer rim of this area is notched as shownat 102 so that pressure can gain access to the area when said rimcontacts the cap 90.

Parts 101, 103 and 107 constitute a double-acting plunger. The plungeris held up (under vented conditions to be described) by a spring 104reacting from a shoulder 105 in body 89 and to a collar 106 on head 107.The cap 90 forms a stop for determining the normal position of theplunger with its piston 101 in the mid cylindrical portion 99. Thisnormal position of the piston 101 is just above a lower port 109connecting with the outlet nipple 83. Port 109 is above what will bereferred to as an injection chamber 116. The piston in said normalposition is also just below an inlet port 113 leading from nipple 79. At115 is shown an upper stepped chamber, one of the steps of which formsthe shoulder 105 upon which spring 104 rests. Entering pressure reachesthe top of head 107 to drive down the piston 101 into the lower chamber116 while retracting the plunger parts 103, 107 from the upper chamber.This compresses spring 104. When this pressure is released the springpushes the piston 101 up'frorn chamber 116 and into the mid cylinder 99,at the same time driving the plunger parts 103, 107 back into chamber115. Each of the screw couplings 94 connects an outlet nipple 83 of apreceding injector 81 with the inlet fitting 79 of the next succeedinginjector asshown in FIGS. 1 and 4.

The last coupler 94 in the series connects with the inlet 85 of theaccumulator 87, details of which appear in FIG. 4. This includes ahollow threaded cap 119 forming a pocket 120 for a spring 121. Thespring reacts from cap 119 to a collar 123 on a plunger 125, the latterslidably fitting a cylindrical portion 127. A signal stem 129 projectingfrom plunger 125 is movable in and out through an opening 131 in the cap119. Pressure on the end 133 of plunger 125 pushes it in to providepressurized lubricant-receiving space 134 in the inlet 85. When pressureis relieved, the spring 121 returns plunger 125 to return the contentsof this space 134 back to the last of the series of injectors underconditions described below. The limiting position of the plunger 125 inspace 134 is determined by engagement of the collar 123 on shoulder 124.Its other limiting position is determined by the point at which thespring 121 bottoms out upon compression. The plunger 125 is thusarranged to provide the same lubricant displacement as that of eachinjector piston 101 in its chamber 116 below its port 109. Instead ofbottoming spring 121 to limit the position of plunger 125, other stopmeans may be used.

Injection operation is as follows, referring to FIGS. -7:

The stippling in FIG. 5 indicates a primed starting condition of eachinjector of the system at low lubricant pressure, as when air pressureis relieved in line 11 by action of timer 5 deexciting solenoid 3 so asto shut air valve 1 and allow it to bleed air line 11. The pump 9 andaccumulator 87 are then as shown in FIGS. 2 and 4 respectively. Checkvalve 73 holds this low pressure.

In time the switch 5 causes solenoid 3 to open valve 1 as its reliefport closes. This forces up the pump piston 17 and its plunger 21 (FIG.2) to force lubricant under pressure past the sleeve 72 to line 77. Thispressure is conveyed to the first injector in the series as shown inFIG. 6. The arrows on FIG. 6 illustrate the action, pressure beingadmitted through upper port 113 above piston 101 forcing it down intothe discharge chamber 116, thereby ejecting lubricant under pressurethrough its check valve 97 to its line 93 leading to the bearing whichit serves. As plunger 101 descends below the lower port 109, pressure isdelivered to the upper chamber 115 of the next succeeding injector inthe series via its inlet port 113. This succeeding injector repeats theaction of the preceding injector (as in FIG. 6) to supply lubricant toits branch bearing supply line 93. The injection action as illustratedin FIG. 6 is repeated sequentially throughout all of the injectors inthe series until the last injector, through its lower port 109, suppliesthe accumulator 87, forcing out the plunger 125 to accumulate the lastlubricant charge in space 134 while raising the signal stem 129 to showthat the cycle has been successfully completed. If the signal stem 129does not appear, this is an indication of trouble in the systemrequiring investigation and correction. In either event the pump 9stalls when the maximum lubricant pressure of which it is capable isreached. The system then remains static under pressure until the timerswitch 5 causes solenoid 3 to close valve 1 and vent the air line 1 1.

When the air line 11 is vented, pump piston 17 and plunger 21 descendunder return action of its spring 19. This permits entry into itscylinder 25 of lubricant through its ball check valve 73, whereby thepressure is relieved first above the piston 101 of the first injector inthe series (FIG. 7 lts spring 104 lifts its plunger 10], 103, 107) backinto compartment 115 to drive lubricant back through upper port 113 topump cylinder 25 via ball check valve 73. Lifting of the piston I01uncovers lower port 109 which admits to compartment 116 a measuredamount of lubricant from the compartment 115 of the next injector inline. This action is repeated in sequence through all of the injectors,the last one receiving lubricant back into its compartment 116 from theaccumulator 87 under action of spring 121. The injector system is thenback in the condition illustrated in FIG. 5. In the following claimscompartment 115 is referred to as a first compartment and compartment116 as a second compartment.

Thus it will be seen that the injectors discharge serially and alsorecharge serially after an injection cycle, only the first onedischarging back to the pump and the last one receiving its measuredamount of lubricant from the accumulator.

The interval over which switch 5 causes valve 1 to be held shut shouldbe made long enough for all injectors of a series to operate throughoutan injection cycle. Thus a greater number of injectors in a series willrequire more time. Other than this, the timing is not critical. Afterinjection the system may be held for a time as long or as short asdesired under pressure maintained by the pump under stall conditionuntil pressure release effected by closing valve 1 and venting line 11.

It is to be understood that the spring of the ball check valve 1 73 inpump 9 is designed to let its ball open in response to a pressure dropacross it under return flow of lubricant which is on the order of 25 to'75 p.s.i. or so. Thus the pressure of the system in normal conditionbetween cycles (FIG. 5) is on that order. The springs of the ball checkvalves 97 in the injectors 81 are designed to hold their balls shutunder return flow of lubricant under pressure involved in recharging(FIG. 7). They also assure prompt closure of check valves when thepistons 101 rise so that no substantial amount of lubricant will bedrawn back from the bearing supply lines 93.

Referring to FIG. 5, the distance D is a measure of the stroke of piston101 and of the length of the compartment 116. Thus it is apparent thatthe measured volumetric discharge upon each downward piston stroke (FIG.6) is substantially nrD wherein r is the piston radius. An equal volumeis at this time received above the piston which, when the pistonreturns, is vented out of compartment 115 to charge lubricant into thelower compartment 116 of the adjacent injector (FIG. 7) to make it readyfor its next injection event. Thus all injectors vent to one another,except, the first one which vents back to the pump through the lubricantfeed line 77. This accounts for the saving in vent line costs inaddition to the reduction in cost by use of only a single accumulatorand malfunction indicator such as 87. It is to be understood that thesimultaneous volumetric displacements of pistons 101 into and out of thechambers 116 and 115 are equal, and that the volumetric displacement ofthe plunger 125 of accumulator 87 becomes equal to each of them aspressure builds up and releases.

As pointed out above, the injector and the accumulator are characterizedby the absence therein of any elastomeric or like sealing parts whichmight be damaged by heat. Although there are such parts in the pump, asshown in FIG. 2, it will be understood that, unlike the injectors andthe accumulator, the pump is mounted at some distance from the quiteoften hot machinery in or upon which the injectors and accumulator aremounted and by reason of which it is undesirable for them to includesuch parts.

It will be appreciated that although the accumulator which isillustrated operates to receive and return fluid by means of aspring-backed piston, an equivalent well-known resilient diaphragm typeof accumulator may be employed.

Although the invention is described for use in injecting lubricants, itis applicable to the injection of other fluids presenting problemsanalogous to those arising in the case of lubricant injection.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A fluid injector comprising,

a hollow manifold forming a. an internal cylindrical portion, with b. apressurizable and venting compartment extending from one end of thecylindrical portion, a first fluid port in said venting compartmentadjacent said one end of the cylindrical portion, through which saidcompartment may be pressurized or vented, and

c. an injection compartment extending from the other end of saidcylindrical portion, said injection compartment having a second portclosely adjacent said other end of said cylindrical portion throughwhich fluid may be moved into the injection compartment or fluid movedout from the venting compartment, said injection compartment in additionhaving an outlet check valve for outward irreversible flow of fluid fromthe injection compartment;

a reciprocable piston in said cylindrical portion, stop means forlocating the piston at a normal position in said cylindrical portionbetween said ports so that the injection compartment communicates withsaid second port,

resilient means for urging the piston toward the venting compartment andto said normal position under a normal pressure in said ventingcompartment thereby to vent the venting compartment through said firstport,

said piston under pressure substantially above normal in the ventingcompartment moving into the injection compartment to a point below saidsecond port, whereby fluid is injected through said outlet check valvefrom the injection compartment and whereby fluid under pressure maytransfer from said first port, through the venting compartment and tosaid second port.

2. A fluid injector according to claim 1, wherein the volumetricdisplacements of the piston are the same in moving to and from saidinjection and venting compartments.

3. A fluid injector system for use with a fluid pump, a fluid pressuresupply line leading from the pump, timed means for intermittentlystarting and stopping the pump intermittently to pressurize said supply,means for venting said line during stoppage of the pump, a variablevolume accumulator having a port for the reception and return therefromof fluid, a series of injectors made according to claim 1, fluidtransmission means connecting the second port of each preceding injectorin the series to the first port of each succeeding injector in theseries except the last, the second port of which is connected to saidport of the accumulator by fluid transmission means, fluid transmissionmeans connecting the pressure supply line from the pump with the firstport of the first injector of the series, an accumulator, and amalfunction indicator means forming part of the accumulator and movablein response to variable fluid volume therein.

4. A fluid injector system for use with a fluid pump, a fluid pressuresupply line leading from the pump, timed means for intermittentlystarting and stopping the pump intermittently to pressurize said supply,means for venting said line during stoppage of the pump, a variablevolume accumulator cylinder having a reciprocating piston therein andhaving a port for the reception into the cylinder and return therefromof fluid under action of said piston, resilient means biasing theaccumulator piston toward the accumulator port, a series of injectorsmade according to claim 1, fluid transmission means connecting thesecond port of each preceding injector in the series to the first portof each succeeding injector in the series except the last, the secondport of which is connected to said port of the accumulator by fluidtransmission means, and fluid transmission means connecting the pressuresupply line from the pump with the first port of the first injector.

5. A fluid injector comprising,

a hollow manifold forming a. an internal cylindrical portion, with b. apressurizable and venting compartment extending from one end of thecylindrical portion, a first fluid port in said venting compartmentclosely adjacent said one end of the cylindrical portion through whichsaid compartment may be pressurized or vented, and

c. an injection compartment extending from the other end of saidcylindrical portion, said injection compartment having a second portclosely adjacent said other end of said cylindrical portion throughwhich fluid may be moved into the injection compartment or fluid movedout from the venting compartment, said injection compartment in additionhaving an outlet check valve for outward irreversible flow of fluid fromthe injection compartment;

a piston movable in said cylindrical portion and forming part of areciprocable plunger, an extending part of the plunger projecting intosaid venting compartment,

a stop for the plunger locating it at a normal position wherein saidpiston is located in said cylindrical portion between said ports wherebythe injection compartment communicates with said second port,

resilient means for driving the plunger into the venting compartmentagainst said stop under a normal pressure in said venting compartment tovent the venting compartment through said first port,

said plunger under pressure substantially above normal in the ventingcompartment moving therefrom, thereby to force said piston from saidcylindrical portion into the injection compartment to a point below saidsecond port, whereby fluid is injected through said outlet from theinjection compartment and fluid under pressure may transfer from saidfirst port, through the venting compartment and to said second port.

6. A lubricant injection system for use with a timed lubricant pump,comprising a series of manifolds each of which has a first and a secondcompartment, said compartments of each manifold being separated by acylinder fitted with a reciprocable piston having a normal position insaid cylinder and movable away from the first compartment and into thesecond compartment or reversely out of the second compartment toward thefirst compartment,

said piston in a nonnal position lying between spaced first and secondports, the first one of which connects with the first compartment andthe second one of which when the piston is in normal position connectswith the second compartment,

said piston in its movement from normal position and into the secondcompartment crossing said second port to connect the port with the firstcompartment,

said second compartment having an outlet for connection with aninjection line and a check valve in said outlet,

a hollow accumulator having an inlet communicating with a cylindertherein, a reciprocable accumulator piston in the accumulator cylinderfor the reception and expulsion of fluid from and to said inlet, meansbiasing the accumulator piston toward the accumulator inlet,

a fluid connection between said pump and the first port of the firstmanifold in the series,

a fluid connection between the second port of the first and every othermanifold in the series and with the first port of the next manifold inthe series, and

a fluid connection between the second port of the last manifold in theseries and the inlet of the accumulator.

7. An injector according to claim 6 including stop means limitingmovement of each manifold piston from the second compartment of itsmanifold, and wherein the volumetric displacement of the accumulator isat least equal to that of each manifold piston in the second compartmentof its injector.

8. An injector according to claim 6 including stop means limitingmovement of each injector piston from the second compartment of itsinjector and wherein the volumetric displacements of the accumulatorpiston and of each injector piston in the second compartment of itsinjector are equal.

9. An injector according to claim 8 wherein each injector pistoncompletely empties the second compartment of its injector in moving intoit.

10. An injector according to claim 9 including signal means operable bythe accumulator piston to indicate when the accumulator cylinder hasbeen filled.

1. A fluid injector comprising, a hollow manifold forming a. an internalcylindrical portion, with b. a pressurizable and venting compartmentextending from one end of the cylindrical portion, a first fluid port insaid venting compartment adjacent said one end of the cylindricalportion, through which said compartment may be pressurized or vented,and c. an injection compartment extending from the other end of saidcylindrical portion, said injection compartment having a second portclosely adjacent said other end of said cylindrical portion throughwhich fluid may be moved into the injection compartment or fluid movedout from the venting compartment, said injection compartment in additionhaving an outlet check valve for outward irreversible flow of fluid fromthe injection compartment; a reciprocable piston in said cylindricalportion, stop means for locating the piston at a normal position in saidcylindrical portion between said ports so that the injection compartmentcommunicates with said second port, resilient means for urging thepiston toward the venting compartment and to said normal position undera normal pressure in said venting compartment thereby to vent theventing compartment through said first port, said piston under pressuresubstantially above normal in the venting compartment moving into theinjection compartment to a point below said second port, whereby fluidis injected through said outlet check valve from the injectioncompartment and whereby fluid under pressure may transfer from saidfirst port, through the venting compartment and to said second port. 2.A fluid injector according to claim 1, wherein the volumetricdisplacements of the piston are the same in moving to and from saidinjection and venting compartments.
 3. A fluid injector system for usewith a fluid pump, a fluid pressure supply line leading from the pump,timed means for intermittently starting and stopping the pumpintermittently to pressurize said supply, means for venting said lineduring stoppage of the pump, a variable volume accumulator having a portfor the reception and return therefrom of fluid, a series of injectorsmade according to claim 1, fluid transmission means connecting thesecond port of each preceding injector in the series to the first portof each succeeding injector in the series except the last, the secondport of which is connected to said port of the accumulator by fluidtransmission means, fluid transmission means connecting the pressuresupply line from the pump with the first port of the first injector ofthe series, an accumulator, and a malfunction indicator means formingpart of the accumulator and movable in response to variable fluid volumetherein.
 4. A fluid injector system for use with a fluid pump, a fluidpressure supply line Leading from the pump, timed means forintermittently starting and stopping the pump intermittently topressurize said supply, means for venting said line during stoppage ofthe pump, a variable volume accumulator cylinder having a reciprocatingpiston therein and having a port for the reception into the cylinder andreturn therefrom of fluid under action of said piston, resilient meansbiasing the accumulator piston toward the accumulator port, a series ofinjectors made according to claim 1, fluid transmission means connectingthe second port of each preceding injector in the series to the firstport of each succeeding injector in the series except the last, thesecond port of which is connected to said port of the accumulator byfluid transmission means, and fluid transmission means connecting thepressure supply line from the pump with the first port of the firstinjector.
 5. A fluid injector comprising, a hollow manifold forming a.an internal cylindrical portion, with b. a pressurizable and ventingcompartment extending from one end of the cylindrical portion, a firstfluid port in said venting compartment closely adjacent said one end ofthe cylindrical portion through which said compartment may bepressurized or vented, and c. an injection compartment extending fromthe other end of said cylindrical portion, said injection compartmenthaving a second port closely adjacent said other end of said cylindricalportion through which fluid may be moved into the injection compartmentor fluid moved out from the venting compartment, said injectioncompartment in addition having an outlet check valve for outwardirreversible flow of fluid from the injection compartment; a pistonmovable in said cylindrical portion and forming part of a reciprocableplunger, an extending part of the plunger projecting into said ventingcompartment, a stop for the plunger locating it at a normal positionwherein said piston is located in said cylindrical portion between saidports whereby the injection compartment communicates with said secondport, resilient means for driving the plunger into the ventingcompartment against said stop under a normal pressure in said ventingcompartment to vent the venting compartment through said first port,said plunger under pressure substantially above normal in the ventingcompartment moving therefrom, thereby to force said piston from saidcylindrical portion into the injection compartment to a point below saidsecond port, whereby fluid is injected through said outlet from theinjection compartment and fluid under pressure may transfer from saidfirst port, through the venting compartment and to said second port. 6.A lubricant injection system for use with a timed lubricant pump,comprising a series of manifolds each of which has a first and a secondcompartment, said compartments of each manifold being separated by acylinder fitted with a reciprocable piston having a normal position insaid cylinder and movable away from the first compartment and into thesecond compartment or reversely out of the second compartment toward thefirst compartment, said piston in a normal position lying between spacedfirst and second ports, the first one of which connects with the firstcompartment and the second one of which when the piston is in normalposition connects with the second compartment, said piston in itsmovement from normal position and into the second compartment crossingsaid second port to connect the port with the first compartment, saidsecond compartment having an outlet for connection with an injectionline and a check valve in said outlet, a hollow accumulator having aninlet communicating with a cylinder therein, a reciprocable accumulatorpiston in the accumulator cylinder for the reception and expulsion offluid from and to said inlet, means biasing the accumulator pistontoward the accumulator inlet, a fluid connection between said pump andthe first port of the first manifold in the series, a fluid connectionbetween the second port of the first and every other manifold in theseries and with the first port of the next manifold in the series, and afluid connection between the second port of the last manifold in theseries and the inlet of the accumulator.
 7. An injector according toclaim 6 including stop means limiting movement of each manifold pistonfrom the second compartment of its manifold, and wherein the volumetricdisplacement of the accumulator is at least equal to that of eachmanifold piston in the second compartment of its injector.
 8. Aninjector according to claim 6 including stop means limiting movement ofeach injector piston from the second compartment of its injector andwherein the volumetric displacements of the accumulator piston and ofeach injector piston in the second compartment of its injector areequal.
 9. An injector according to claim 8 wherein each injector pistoncompletely empties the second compartment of its injector in moving intoit.
 10. An injector according to claim 9 including signal means operableby the accumulator piston to indicate when the accumulator cylinder hasbeen filled.